T-cell recognition of autologous melanoma is vitally dependent on the expression by tumor cells of tumor associated antigens in the context of self MHC class I encoded gene products. In both murine and human studies, transduction with the gene for gamma-IFN increases the surface membrane expression of these important molecules by the tumor cells and results in dramatic improvement of T-cell responses following stimulation with the modified tumor cells. The enhanced response is directed not only toward modified tumor cells, but against the unmodified tumor cells as well. The goals of this proposal are to examine the T-cell responses following stimulation with autologous tumor cells which have been modified by transduction with the gene for human gamma-IFN. We will determine the changes in the level of expression of HLA class I molecules on the surface of the gene modified tumor cells and examine the changes in T-cell activation and recognition of parental and gamma-IFN gene modified tumor cells using cytotoxicity, blastogenesis, and elaboration of immune cytokines by the T-cells. In a model system in which expression of the HLA-A2 restricting allele is down regulated by the tumor cells, we will examine the effects following re-expression of this allele subsequent to transduction with the gene for human gamma-IFN. We will also examine in this system unique (public?) restriction patterns of autologous melanoma specific HLA class I restricted cytotoxic T-cells which share no serologically defined class I molecules with their melanoma tumor targets. We will also examine the modification of tumor specific immune status in patients undergoing active immunization with a vaccine prepared from ~-IFN gene modified autologous tumor cells.